Recently, from the viewpoint of reduction in environmental load, eco-friendly and clean liquid fuels in which the contents of sulfur and aromatic hydrocarbons are small have been demanded. From such a viewpoint, as a technique for producing raw material hydrocarbons in order to produce a base stock for fuel oil that contains no sulfur or aromatic hydrocarbons and is rich in aliphatic hydrocarbons, particularly, a base stock for kerosene and gas oil, a method using a Fischer-Tropsch synthesis reaction (hereinafter, referred to as the “FT synthesis reaction” in some cases) in which carbon monoxide gas and hydrogen gas are used as raw materials has been examined.
Moreover, a technique in which synthesis gas mainly containing carbon monoxide gas and hydrogen gas is produced by reforming of a gaseous hydrocarbon raw material such as natural gas, a hydrocarbon oil (hereinafter, referred to as the “FT synthetic oil” in some cases) is synthesized from the synthesis gas by the FT synthesis reaction, and further, through an upgrading section that is a section of hydrotreating the FT synthetic oil to produce a variety of base stocks for liquid fuel oil, a base stock for kerosene and gas oil and naphtha or a wax and the like are produced is known as a GTL (Gas To Liquids) process (see Patent Literature 1 described below, for example.).
As a synthesis reaction system that synthesizes a hydrocarbon oil by the FT synthesis reaction, for example, a slurry bubble column FT synthesis reaction system that blows synthesis gas into a slurry, in which solid catalyst (hereinafter, referred to as the “FT synthesis catalyst” in some cases) particles having activity to the FT synthesis reaction are suspended in a hydrocarbon oil, to perform the FT synthesis reaction is disclosed (see Patent Literature 2 described below, for example.).